This invention generally relates to garment cleaning apparatuses and methods, and is specifically concerned with a continuous circulation water wash which more effectively removes particulate radioactive contaminants from the garments worn by maintenance personnel who service nuclear power facilities.
Machines for cleaning radioactively contaminated clothing are known in the prior art. Such prior art clothing may use either a dry cleaning technique or a water wash technique to achieve the desired end. Of the two techniques, dry cleaning with the use of fluorocarbon solvents such as Freon.RTM. is presently preferred over known water wash type machines due to the generally superior penetrating ability of fluorocarbon solvents. However, before the relative advantages and disadvantages of these two types of techniques can be fully appreciated, some background of the nature of the clothing cleaned and the environment wherein it is used is necessary.
Present-day nuclear power facilities require various maintenance and operating personnel to work in areas which may be contaminated with radioactive particles. To prevent these radioactive particles from coming into contact with the skin of such personnel, protective clothing in the form of frocks, hoods and shoe coverings (known as "duck feet" in the art) are worn. After use, it is essential that the clothing be cleaned in such a way that removes substantially all of the radioactive particulates, and all or at least most of the conventional soils, sweats and body salts that also accumulate therein. The removal of certain rare but highly radioactive particulates, such as the "fuel fleas" which may be generated by the cracking of a fuel rod, is particularly important as such particles are capable of exposing a small, pinpoint area of skin to a dangerous level of radioactivity. However, the cost of performing such a cleaning must be substantially less than the cost of replacing the garment if the cleaning is to be cost effective. If the cost of cleaning approaches the cost of disposing of the old garment and replacing it with another, then garment replacement becomes preferable to garment cleaning.
Dry cleaning techniques for cleaning such radioactively contaminated clothing are presently in greater use than water wash techniques due to the inherently lower surface tension and hence generally superior penetrating ability of the fluorocarbons used in such techniques. While such fluorocarbons have proven effective in removing substantially all of the radioactive particulates from the clothing, these dry cleaning techniques are not without shortcomings. For example, the fluorocarbons used can dissolve the elastomers in synthetic rubbers that form parts of boots and other shoe coverings used in maintenance operations. The dissolution of these elastomers causes the synthetic rubbers to become brittle and to crack, thereby damaging and ultimately destroying the particular article of clothing containing the synthetic rubber. Other materials used in protective clothes and shoes such as Neoprene.RTM. tend to soak up and absorb these fluorocarbons until unacceptable levels of these fluorocarbons build up in the articles of clothing. These excess fluorocarbons can be dried out of the clothing by the application of additional amounts of heat. However, the addition of such a dry-out step in the cleaning process adds to the overall expense of cleaning, and may tend to heat damage the plastic and rubber portions of the clothing, thereby defeating the purpose of the extra dry-out. Still another shortcoming associated with dry cleaning techniques is the limited ability of fluorocarbons to dissolve sweat and body salts. Even though the fluorocarbons may succeed in removing substantially all of the radioactive particulates, the accumulation of such sweat and body salts will ultimately give the garment a cumulative "locker room" odor. Worse yet, these fluorocarbons are limited (as are most organic solvents) in their ability to dissolve and to remove radioactive contaminants in the form of metallic salt, such as cesium 137. Finally, all known devices which clean such clothing by means of fluorocarbons release significant amounts of these fluorocarbons into the air, which may be damaging to the layer of ions in the atmosphere which blocks ultraviolet radiation of the sun. This last problem has induced the U.S. Environmental Protection Agency to promulgate new regulations which will become effective in 1989 that substantially restrict the use of such fluorocarbons.
While wet washing techniques avoid many of the aforementioned shortcomings associated with dry cleaning techniques, they too have their drawbacks, the most serious being the generation of a water effluent which contains the radioactive particles removed from the clothing. The transportation and disposal of such an effluent significantly contributes to the cost of the wash, notwithstanding the fact that the effluent qualifies as low radioactive waste. Even though most nuclear facilities have on-site demineralizer systems which are capable of decontaminating such water, the inconveniences and expenses associated with the use of such on-site demineralizer systems also add substantially to the overall cost of such prior art water wash techniques. Still another problem is the relatively lower efficiency of the water used in such systems in penetrating the fabrics that form such clothing. The relatively lower penetrating ability of water coupled with the greater effort needed for dry out due to the lower volatility of water as compared to Freon.RTM. generally has the negative effect of increasing the time necessary to effectively water wash a contaminated garment.
To address these concerns, Westinghouse Radiological Services, Inc., (a wholly owned subsidiary of the Westinghouse Electric Corporation) has developed an improved water wash system which utilizes hydraulically isolated wash and rinse-water systems that include water polishers for providing demineralized and filtered water to a washing machine for every wash cycle and rinse cycle. This invention is described and claimed in co-pending U.S. Pat. application Ser. No. 162,454, filed Mar. 1, 1988 and assigned to the Westinghouse Electric Corporation, the entire specification of which is expressly incorporated herein by reference. While this water wash system and method represents a substantial advance in the art, it, too has a shortcoming which limits its effectiveness in removing radioactive particles from the garments that it washes. Specifically, the applicants have observed that the amount of particulate contaminants which are removed from the garments during each wash or rinse cycle is significantly less than the amount of particulate contaminants that the surfactants in the wash-water actually dislodge from the fabric forming the clothing.
Clearly, there is a need for the garment washing apparatus and method which retains all of the advantages associated with the latest water wash system, but which is more effective in removing radioactive particles from the interior of the washing machine once they are dislodged from the garments so that they will not re-lodge back into the garments at the termination of a wash or a rinse cycle. Such a device would have the ability to render a garment free of such particulate contaminants with a minimum number of wash and rinse cycles, and in a minimum amount of time.